PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.CLARKS COLLECTION Women's Black Leather Slip On Comfort Flats Shoes Size 7.5MAnne Klein Womens Career Shoes Low Heel Sz 6M Mamollie Black Sharp Style WorkRialto Shirlee Flats Women's Size 8.5 M, Champagne PRE OWNED D6202 , sami-27 Slip On Casual Party Flats Office Winter Warn Women's Shoes Black 7^ , CUTE COMFY Women's Black Patent Leather Via Spiga Heeled Loafers Heels Shoes 5 , Dr. Scholl's Madi Faux Leather Mule Sneakers, Women's Size 9M, Black , Lady Stork Black and Gold FltasCole Haan Nantucket Camp Moc Women's Beige/Navy Moccasin Boat Shoe Loafers Sz 9J41 Adventure On~Brown Jasper~Ladies Shoes Size 11 EUC Women'sEarth "Charm" Brown Leather Slides/Mules Kalso Size 11 Womens 9 Men 41/42 EUFarylrobin x Free People Womens Geo Plains Sandals Shoes White Size 11 NewAmalfi by Rangoni Womens Matta Closed Toe LoafersNEW Rockport M77349 Shore Bets Seaworthy II Loafers, Women's Ivory - Choose SizeWomen's Fashion Running High Top Sneakers Casual Athletic Walking Sports Shoes , Easy Street Women's KANA Mule, Blue/Green Leaf Fabric, 8 N US , Vince. Warner Brown Womens Shoes Size 8.5 M Flats MSRP $225Naturalizer Womens Manor Black Fashion Sneakers Shoes 6.5 Medium (B,M) BHFO 5730Saucony Womens Raptor TR7 Trail Running HIking shoes SZ 8.5 f844SKECHERS WOMENS GRATIS CLOUD -UP TO SPEED MEMORY FOAM /NVYWomen's SUEDE MONO ICE CORAIL Good Design Athletic ShoesWomen's Pleaser Women's Gala 01 Clear/Clear Beautiful Design Athletic ShoesWomen's Under Armour Women's Speedform Slingwrap Elegant Shape Athletic Shoes , Propét Women's Chickadee Maize 7.5 M , Pomeranian Dots Print Slip Ons For Women-Express Shipping , SHIHWEISPORT ASICS T3N7N-0136 KAYANO 20 RUNNING SHOE FOR WOMAN *FINAL SALE* , Bombay Cat Print Running Shoes For Men-Free Shipping , ASICS GT-2000 5 Trail Running Shoes - Women's Size 8, Aluminum/Silver/OrchidNew Women`s Keen Versatrail Low Hiking Shoes MSRP$120 , DREW Women's PARADISE II Walking Shoe White Leather Size 9 W (14521-22) , Converse Targa XLT, Chuck Taylor, Size 9. ,
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."